Processor-controlled light-admitting heliostat

ABSTRACT

A heliostat optimized to be positioned near a skylight or other aperture is disclosed. The heliostat comprises a plurality of reflective elements arranged in a substantially planar array, each element being mounted so as to be rotatable about a longitudinal axis of rotation. A first motor rotates the array about an axis substantially perpendicular to the plane of the array; and a second motor rotates the reflective elements about their respective axes of rotation. A processor provides control signals to operate the first motor as required to orient the array such that the respective axes of rotation of the reflective elements are substantially perpendicular to an azimuth to the sun and to operate the second motor as required to rotate the reflective elements about their respective axes of rotation to position the reflective element to reflect the sun&#39;s light to a target area.

CROSS-REFERENCE TO OTHER APPLICATIONS

This application is a continuation-in-part of co-pending U.S. patentapplication Ser. No. 12/891,489 entitled LIGHT-ADMITTING HELIOSTAT filedSep. 27, 2010, which is incorporated herein by reference for allpurposes.

BACKGROUND OF THE INVENTION

A heliostat typically includes one or more mirrors or other reflectivesurfaces the position and/or orientation of which are moved so as tokeep reflecting sunlight toward a predetermined target despite the sun'sapparent motions in the sky. Typically the target is stationary and thesun's light is reflected in a constant direction.

Some heliostats actively track and follow the sun, for example usinglight sensors. Others are controlled by a computer. The computer isgiven the latitude and longitude of the heliostat's position on theearth and the time and date. From these, using astronomical theory, thecomputer calculates the direction of the sun as seen from the mirror,e.g. its compass bearing (azimuth) and angle of elevation. Then, giventhe direction of the target, the computer calculates the mirrororientation required to reflect the sun's light to the target, and sendscontrol signals to motors, such as stepper motors, so they turn themirror to the correct alignment. This sequence is repeated to keep themirror properly oriented.

Heliostats have been used in solar power applications, to direct thesun's light continuously onto a photovoltaic or other solar cell. Theyalso have been used in daylighting, i.e., using reflected sunlight toilluminate interior or even exterior spaces. For example, heliostatshave been used to direct reflected sunlight into interior spaces, suchas into a building through a window or skylight. In such uses, typicallythe heliostat has been positioned outside the window or skylight andused to direct reflected sunlight, for example at a perpendicular orother constant angle, into an interior space through a window, askylight, or a solar tube or other indirect path. Such externalheliostats are exposed to the elements and may require roof penetrationsto mount them. In addition, external heliostats may not be practical ordesired for use with preexisting skylights or windows.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention are disclosed in the followingdetailed description and the accompanying drawings.

FIG. 1 is a block diagram illustrating an embodiment of a heliostat.

FIGS. 2A and 2B are block diagrams illustrating embodiments of aheliostat.

FIG. 3 is a block diagram illustrating an embodiment of a heliostat.

FIG. 4 is a block diagram illustrating an embodiment of a heliostat.

FIG. 5 is a block diagram illustrating an embodiment of a heliostat inthree positions at different times of day.

FIG. 6 is a block diagram illustrating an embodiment of a heliostat.

FIG. 7 is a block diagram illustrating the relationship between tiltangle and altitude of the sun in the special case in which light isdesired to be reflected straight down.

FIG. 8 is a block diagram illustrating an embodiment of a heliostatcontrol system.

FIG. 9 is a flow diagram illustrating an embodiment of a process forcontrolling a heliostat.

FIG. 10 is a block diagram illustrating an embodiment of a heliostat.

FIG. 11 is a block diagram illustrating an embodiment of a set ofmirrors.

FIGS. 12A and 12B are block diagrams each illustrating an embodiment ofa set of mirrors.

DETAILED DESCRIPTION

The invention can be implemented in numerous ways, including as aprocess; an apparatus; a system; a composition of matter; a computerprogram product embodied on a computer readable storage medium; and/or aprocessor, such as a processor configured to execute instructions storedon and/or provided by a memory coupled to the processor. In thisspecification, these implementations, or any other form that theinvention may take, may be referred to as techniques. In general, theorder of the steps of disclosed processes may be altered within thescope of the invention. Unless stated otherwise, a component such as aprocessor or a memory described as being configured to perform a taskmay be implemented as a general component that is temporarily configuredto perform the task at a given time or a specific component that ismanufactured to perform the task. As used herein, the term ‘processor’refers to one or more devices, circuits, and/or processing coresconfigured to process data, such as computer program instructions.

A detailed description of one or more embodiments of the invention isprovided below along with accompanying figures that illustrate theprinciples of the invention. The invention is described in connectionwith such embodiments, but the invention is not limited to anyembodiment. The scope of the invention is limited only by the claims andthe invention encompasses numerous alternatives, modifications andequivalents. Numerous specific details are set forth in the followingdescription in order to provide a thorough understanding of theinvention. These details are provided for the purpose of example and theinvention may be practiced according to the claims without some or allof these specific details. For the purpose of clarity, technicalmaterial that is known in the technical fields related to the inventionhas not been described in detail so that the invention is notunnecessarily obscured.

A heliostat suitable use for daylight or other applications isdisclosed. In some embodiments, the heliostat includes a set ofsubstantially rectangular reflectors arranged in a louver-like array.The array of reflectors is mounted in a ring or other housing, in aposition such that the respective longitudinal axes of the reflectorslie substantially in one or more planes perpendicular to a central axisof the housing, such as an annular axis of a ring housing. The housingis rotatably mounted on a frame. A first stepper motor or other drivemechanism is responsive to control inputs to rotate the housing so as toorient the array so that the respective longitudinal axes of therespective array elements are perpendicular to the direction of the sun.A second stepper motor or other drive mechanism is responsive to controlinputs to rotate the array elements about their respective longitudinalaxes to achieve a tilt angle required to receive the sun's light througha skylight or other window, at varying angles as the apparent angle ofelevation of the sun changes through the day, and reflect the receivedlight to a stationary or other target.

FIG. 1 is a block diagram illustrating an embodiment of a heliostat. Inthe example shown, sunlight enters an interior space through a skylightor other window 102 positioned in an opening in a roof or other outershell structure 104 or interior space 106. Sunlight enters the skylight102 from varying compass directions and at varying apparent angles ofelevation as the sun appears to move through the sky in the course ofthe day. A heliostat 108 directs reflected light of the sun toilluminate a target area 110. In some embodiments, the heliostat iscomputer-controlled and changes the orientation of an array of mirrorsor other reflectors as the sun appears to move through the sky toreflect light in a constant direction, in this example straight down, toilluminate the target area 110. In various embodiments, the heliostatmay be configured to illuminate any desired target, for example adiffuser to fill the interior space 106 with diffuse light; a userindicated target to which the reflected light of the heliostat has beenpointed by a user, for example using a remote or other control device,and onto which a control system of the heliostat has locked position; areflector or other device configured to further direct the lightreflected by the heliostat to a further target; or any other target.

FIGS. 2A and 2B are block diagrams illustrating embodiments of aheliostat. In the example shown in FIG. 2A, the heliostat 108 ispositioned relatively near to the skylight 102. As a result, the sun'slight, represented in FIG. 2A by arrows 202 and 204, entering throughskylight 102—even at the shallow angle shown—reaches a relatively largeportion of the upper surface area of the heliostat 108. By contrast, asseen in FIG. 2B if the heliostat 108 is positioned further away from theskylight 102, in this example approximately twice the distance, lightthat formerly struck the heliostat in the example shown in FIG. 2A nolonger does, as shown by the dotted line indicating the path of lightassociated with arrow 202. As a result, the sun's light reaches directlyonly about the left half of the upper surface of heliostat 108 in theexample shown in FIG. 2B. In various embodiments, therefore, the sizeand/or number of mirrors or other reflective elements comprisingheliostat 108 is selected at least in part to enable the heliostat 108,and in particular the mirrors or other reflectors comprising heliostat108, to be positioned as near as possible to the skylight or otherwindow 102, i.e., as near as possible without having the mirrors orother reflectors be prevented by contact with skylight 102 or any otherstructure from being moved into a position (e.g., a tilt angle) requiredto reflect light to the target. Doing so maximizes the total reflectivesurface area that can be used to reflect the sun's light to the desiredtarget.

FIG. 3 is a block diagram illustrating an embodiment of a heliostat. Inthe example shown, the heliostat 300 is viewed from the top (or bottom).Heliostat 300 comprises a ring or other annular housing 302 and an arrayof rectangular mirrors 304. Each rectangular mirror 304 is mounted on aset of left and right brackets 306 in a manner that allows the mirrors304 to be rotated about their respective longitudinal axes, e.g., toachieve a tilt angle required to reflect the sun's light to a target. Astepper motor or other drive mechanism 308 is responsive control signals(not shown) to position the mirrors 304 at a required tilt angle, e.g.,such that a perpendicular to the reflective surface of the mirrorbisects an angle formed by the sun, the reflective surface, and thetarget. In some embodiments, transmission elements not shown in FIG. 3,such as gears, wheels, rollers, belts, etc. are housed in and/or mountedon brackets 306 to transmit the rotational movement and force of a shaftof motor 308 to rotatable longitudinal shafts or other elements used tomount mirrors 304 to brackets 306.

In the example shown in FIG. 3, housing 302 comprises a rotatablymounted ring. A nylon or other roller 310 driven by a second stepper orother motor, not shown, rotates the housing 302 as required to maintainthe array of mirrors 304 in a position such that the respectivelongitudinal axes of the mirrors 304 are substantially orthogonal to acompass direction to the sun. In this way, the array of mirrors 304 arerotated about the annular (vertical, in the example shown in FIG. 1 forexample) axis of the housing 302 to continually face the compassdirection of the sun and the mirrors are tilted to an angle, based onthe altitude of the sun as it appears to move first higher then lowerthough the sky, such that the sun's light is reflected through the dayonto the desired target.

In some embodiments, the heliostat is mounted to be as near as possibleto a skylight or other aperture. In the case of a skylight or otheraperture in a pitched or other non-horizontal roof, the heliostat maynot be mounted horizontally and the pitch angle and direction of theskylight or other aperture, and hence the heliostat if mounted parallelthereto, are provided as inputs to the heliostat's control system,described more fully below, to enable the angular position of the arrayand the tilt angle of the mirrors required to maximize the amount ofsunlight that is scooped and redirected to the target area, given thechanging position of the sun, to be computed. In some embodiments, anaccelerometer is used to sense the pitch angle at which the heliostathas been mounted.

In various embodiments, the heliostat 300 is mounted relatively verynear a skylight or other window. In some embodiments, the dimension ofthe mirrors and other components of the heliostat are selected to allowthe heliostat to be positioned as near as possible to the skylight orother window, to allow the maximum amount of sunlight possible to bescooped and redirected to the target area, even when the sun is at lowangles of incidence. The close proximity to the skylight and associatedheat and moisture, particularly in some climates, may make the heliostat300 susceptible to corrosion. Therefore, in some embodiments elements ofheliostat 300 are made of stainless steel or other sufficiently rigidand strong materials that will not corrode or will not corrode much evenin a relatively warm, moist environment.

In various embodiments, the heliostat described herein may be used todirect to the target area light from sources other than the sun, forexample at night, such as moonlight or other natural light, and/or lightfrom a streetlamp or other artificial source.

In some embodiments, a fixed external mirror or other reflector ispositioned outside the skylight or other aperture, e.g., on the northside of the aperture (in the northern hemisphere) to maximize thesunlight reflected to the target during times when the sun's angle ofincidence is low.

FIG. 4 is a block diagram illustrating an embodiment of a heliostat. Inthe example shown, the heliostat 300 of FIG. 3 is mounted in a frame402. In some embodiments, mounting the heliostat in frame 402facilitates installing the heliostat, for example by attaching frame 402to a skylight or window frame and/or to the ceiling or other structurethrough which the skylight or window allows sunlight to pass. In someembodiments, to allow a maximum amount of sunlight to enter a horizontalelement 404 of the frame 402, or at least a portion thereof such as theportion that lies outside housing 302, is made of Plexiglas™ or anothertransparent or translucent polymer, glass, or another sufficiently rigidand strong transparent or translucent material. In some embodiments, theframe 402 is larger than the skylight or other aperture, to maximize themirror area that is exposed to intercept and redirect the sun's rays.

FIG. 5 is a block diagram illustrating an embodiment of a heliostat inthree positions at different times of day. In the example shown,heliostat 300 of FIG. 3 is shown in three positions 300 a, 300 b, and300 c, corresponding to times of day 8 a.m., 11 a.m., and 5 p.m.respectively. At each time of day, the heliostat 300 is shown as havingbeen rotated to maintain a desired orientation of the array of mirrorswith respect to the compass direction to the sun. This enables the sun'slight to be reflected more or less continuously throughout the day ontoa desired target, by tilting the reflectors to an angle such that thenormal to the reflective surface bisects the angle between the sun andthe target.

FIG. 6 is a block diagram illustrating an embodiment of a heliostat. Inthe example shown, the mirrors 304 of the heliostat 300 of FIG. 3 areviewed from the side. The mirrors 304 have been tilted to an angle suchthat the grazing angle θ of the sun's light hitting the reflectivesurface of the mirror is equal to the angle between the reflectivesurface and in this example the vertical (or any other desired directionto a desire target). The angle at which the mirrors 304 are tilted isvaried through the day, as the sun appears to move higher and lower inthe sky, so that the reflected beams 602 are directed more or lesscontinuously onto the desired target.

In various embodiments, the shape of the reflective surfaces may beselected to achieve a desired illumination effect. For example, in someembodiments convex mirror surfaces are used to diffuse the reflectedlight. Conversely, concave mirrors could be used to concentrate thereflected light.

FIG. 7 is a block diagram illustrating the relationship between tiltangle and altitude of the sun in the special case in which light isdesired to be reflected straight down. In the example shown, the mirror304 is tilted to an orientation such that the grazing angle θ of thesun's light hitting the reflective surface of the mirror 304 is suchthat the reflected light is directed straight down onto a target below.In this special case, since the angle the reflected beam makes with thereflective surface of the mirror is by a property of reflection the sameangle θ, and since the angle between the reflected light and thereflective surface also is the same as the tilt angle by which themirror 304 is rotated angularly from the vertical, in this special casethe tilt angle selected to direct the reflected light straight down,plus the grazing angle (in this case the same as the tilt angle), plusthe altitude φ of the sun at any time form a right angle. Therefore insome embodiments the tilt angle θ of the mirrors would be varied asrequired to maintain the relationship 2θ+φ=90°, i.e., the tilt anglewould be set to θ=(90°−φ)/2 and would be adjusted through the day as φvaried with the changing altitude of the sun as it appeared to movethrough the sky.

FIG. 8 is a block diagram illustrating an embodiment of a heliostatcontrol system. In the example shown, a personal computer or othercomputer or processor 802 receives geographic position (e.g., latitudeand longitude), time, and date information from a GPS or other device804. In other embodiments, one or more of the location, time, and dateinformation may be input manually and/or other than from a GPS device.The computer 802 is configured, e.g., by software or otherwise, to usethe position, date, and time information, and astronomical theory, tocompute predicted positions of the sun. In various embodiments, thecomputer 802 computes at a configured interval an azimuth to the sun(e.g., degrees relative to north or some other reference direction) andaltitude or elevation of the sun. The computer 802 uses the computedposition of the sun to determine an orientation of the reflectivemirrors of a controlled heliostat, such as heliostat 300 of FIG. 3,required at any given time to direct reflected light to a configuredtarget. The computer computes and sends to a rotation motor 806 and tiltmotor 808 control signals to cause the motors 806 and 808 to rotate themirror array and tilt the mirrors as required to achieve the desiredorientation.

In some embodiments, computer 802 and/or GPS 804 may comprise a mobilecomputing device, such as a smart phone or tablet. An app may beinstalled on computer 802 to enable the heliostat to be programmed,directed to a target, and/or otherwise controlled. Wireless technologiessuch as Wi-Fi, Bluetooth, infrared, and/or other wireless communicationsmay be used to communicate signals from the computer 802 to heliostat300. For example, computer 802 and heliostat 300 may be on a samewireless network, such as a local network in a home or other building.

In some embodiments, a video camera or other video device is includedand configured to provide video of the target area. The video is used invarious embodiments for surveillance and/or control, for example toprovide to computer 802 visual feedback indicating how well theheliostat is tracking the target area. For example, if light reflectedby the heliostat gradually drifted off target, feedback from the videocamera could be used to detect that condition and, for example,corrective control signals could be computed and/or the heliostat andassociated control system reset.

A power supply 810 provides power to motors 806 and 808. In variousembodiments, the power supply 810 comprises a super-capacitor, battery,or other energy storage device. In some embodiments the power supply ischarged by one or more solar power devices, such as photovoltaic cells,mounted on the heliostat 300, for example on the surfaces opposite thereflective surfaces of mirrors 304. In some embodiments, photovoltaiccells mounted on the heliostat 300 power motors mounted on a samemovable subassembly as the photovoltaic cells and the structures themotors position, eliminating the need for physical structures totransmit power, control signals, and/or motor force from externalstructures to the subassembly. In some embodiments, the photovoltaiccells may charge a battery or other storage device, to provide power foruse at night or other times when the photovoltaic cell output may not besufficient.

Referring further to FIG. 8 in the example shown, the computer 802receives position feedback signals from rotation position sensor 812 andtilt angle 814. In some embodiments, control and/or feedback signals aresent wirelessly. For example, in some embodiments the heliostatcomprises a WiFi or other wireless hub and the computer 802 isconfigured to log into the hub and provide control signals to andreceive feedback signals from the heliostat via the wireless hub. Insome embodiments, rotation position sensor 812 and tilt angle 814comprise mechanical (e.g., detent based), optical, radiofrequency, orother position sensors. In various alternative embodiments, the controlis open loop and rotation position sensor 812 and tilt angle 814 areomitted. In some embodiments, the heliostat may include accelerometers,magnetometers, or other sensors to determine automatically and provideto computer 802 an orientation, e.g., relative to the ground/floor, ofthe heliostat as installed. In various embodiments, incorporating one ormore accelerometers, magnetometers, or other sensor enables theheliostat to determine its orientation automatically. In someembodiments, the heliostat is configured to use its orientation asdetermined using such integrated sensors to program itself to maintainand control the rotational position of the array and the position of thearray elements relative to the sun as disclosed herein.

In some embodiments, a global positioning system (GPS) and/ororientation sensing functionality of a phone or other mobile device maybe used to sense the location and/or orientation of the heliostat. Forexample, in some embodiments, a phone or other mobile app may be used toprogram the heliostat. The phone or other device may be placed flatagainst an angled ceiling or other structure along which the heliostatis or will be installed, and the phone or other device's features may beused to detect the angle and compass orientation of the heliostat. Insome embodiments, the angle may not need to be detected and the app isused to steer the beam of light reflected out by the heliostat to atarget, e.g., inside a house or other structure, enabling the heliostatto be programmed to maintain the beam on the target without firstdetecting or being provided with the angle at which the heliostat isinstalled.

In some embodiments, to conserve energy the computer 802 is configuredto shut down when the heliostat is not in operation, e.g., at night, andto wake up in the morning. In some embodiments, the computer 802 isconfigured to reposition the heliostat only periodically and to shutdown in between. The computer 802 in some embodiments comprises amicrocontroller, mounted in some embodiments on a support structure ofthe heliostat.

FIG. 9 is a flow diagram illustrating an embodiment of a process forcontrolling a heliostat. In some embodiments, the process of FIG. 9 isimplemented on a computer or other processor configured to control aheliostat, such as computer 802 of FIG. 8. In the example shown, theazimuth (direction) and altitude (elevation) of the sun are determined(902). The mirror array orientation required to direct reflected lightof the sun to a target, given the sun's current position, is computed(904). The mirror array is driven to the required array orientation(e.g., rotation about annular axis of heliostat housing) and the mirrorsare driven to the required tilt angle (906). The array remains in theposition to which it has been driven until it is time to update (908),at which time a further iteration of 902, 904, and 906 is performed. Theprocess continues until done (910), e.g., control of the heliostat isturned off until next needed.

In some embodiments, the heliostat is mounted such that a plane of theheliostat is substantially parallel to a skylight or other window oraperture. In the case of a pitched or other non-horizontal roof, theheliostat may not be oriented in a horizontal plane. In some suchembodiments, a computer such as computer 802 of FIG. 8 is pre-programmedwith a pitch angle and direction of the heliostat, and the pitch angleand direction are factored into the computation of the positions towhich the heliostat must be driven to maximize the amount of light thatis scooped and redirected to the target area. In some embodiments, thepitch angle may be detected by the heliostat itself, e.g., usingaccelerometers or other sensors, and provided to computer 802.

FIG. 10 is a block diagram illustrating an embodiment of a heliostat. Inthe example shown, heliostat 1000 includes an annular housing 1002 andan array of mirrors 1004, 1006, 1008, and 1010 mounted in housing 1002in a manner that allows them to be rotated about their respectivelongitudinal axes. The respective shapes of the mirrors 1004, 1006,1008, and 1010 in this example have been selected to maximize thereflective surface area within the confines of the annular housing 1002.Specifically, mirrors 1004 and 1010 have shapes suggestive of thecapital letter “D”, and mirrors 1006 and 1008 have rounded ends thatfollow the curve of annular housing 1002. A roller 1012 is configured torotate housing 1002 and the mirrors 1004, 1006, 1008, and 1010 mountedtherein about a central annular access of housing 1002. A cable drive1014 driven by a motor 1016 and connected to a worm gear or othertransmission mechanism 1018 are configured to adjust the tilt angle ofthe mirrors 1004, 1006, 1008, and 1010. In some embodiments, cable drive1014 and gear 1018 drive a chain or belt that runs down a central axisof the mirror array.

While in the example shown in FIG. 10 a cable drive 1014 andtransmission mechanism 1018 driven by an externally mounted motor 1016are used to adjust the tilt angle of the mirrors, in some embodimentscomponents mounted on and/or within annular housing 1002 are used tocontrol the tilt angle. For example, photovoltaic cells mounted onannular housing 1002 and/or on the mirrors or other structures may beused to power one or more motors mounted on and/or within annularhousing 1002 to control the tilt of mirrors 1004, 1006, 1008, and 1010.

FIG. 11 is a block diagram illustrating an embodiment of a set ofmirrors. In the example shown, mirrors 1100 include mirrors 1104, 1106,1108, and 1110. Each mirror has a cutout in a central region indicatedby arrow 1112 configured to facilitate rotation of the mirrors abouttheir respective longitudinal axes, for example by a chain, belt, orother mechanism.

FIGS. 12A and 12B are block diagrams each illustrating an embodiment ofa set of mirrors. In the example shown in FIG. 12A, mirrors 1204 aremounted on a bracket 1206 at a central longitudinal axis 1208. Themirrors 1204 are narrow relative to their length, allowing the mirrors1204 to be positioned relatively near skylight 1202, since even in thefully vertical position the mirrors 1204 do not extend very far abovethe bracket 1206.

In the example shown in FIG. 12B, wider mirrors 1224 mounted at alongitudinal axis 1228 offset from the center are used. The mirrors inmany geographic locations will not be required to be rotated through afull range of motion, allowing mirrors that extend further in thedownward direction, and therefore having more reflective surface, areato be used. In various embodiments, the mirrors 1224 are not necessarilyof the same width. For example, mirrors expected to remain at the backof the array, further away from the sun than mirrors kept at the front,may be wider, since with respect to those mirrors there is less concernthat they will block light from reaching other mirrors behind them. Insome embodiments, the mirrors may not be mounted on longitudinal axeshaving the same offset from center.

In some embodiments, the mirrors are mounted on brackets rotatablymounted to the heliostat housing. The mirrors may be shifted in thebrackets to a position such that the mirrors rotate about an axis otherthan a central longitudinal axis of the mirror. In some embodiments, themirrors are shifted to a position that allows the heliostat to bepositioned nearer the skylight or other aperture.

While in a number of embodiments described and illustrated herein anarray of four mirrors is described and/or shown, in other embodimentsmore or fewer mirrors may be included in the mirror array. Also, whilerectangular and substantially rectangular mirrors are shown in someembodiments, in other embodiments arrays comprising mirrors of othershapes, such as squares, circles, or other shapes, and two dimensionalarrays having more than one mirror per row, may be used. In addition,although a ring or other circular housing is shown in a number ofembodiments described herein, in other embodiments a rotatable housinghaving another shape may be used, or the array may be held in positionby a structure other than a rotatable housing.

Although the foregoing embodiments have been described in some detailfor purposes of clarity of understanding, the invention is not limitedto the details provided. There are many alternative ways of implementingthe invention. The disclosed embodiments are illustrative and notrestrictive.

What is claimed is:
 1. A heliostat, comprising: a housing; a pluralityof reflective elements arranged in a substantially planar array, eachelement mounted in the housing so as to be rotatable about a first axisof rotation of the element, the respective first axes of rotation beingsubstantially in parallel and lying substantially in a plane orsubstantially parallel to a plane of the array, and each reflectiveelement being of a shape and size such that a distance from the firstaxis of rotation to an outer edge of the reflective element is less thana distance at which the heliostat is configured to be placed on a lightegress side of a fixed light-admitting aperture oriented at an arbitrarypitch and direction; a plurality of shafts coupled to the plurality ofreflective elements, the plurality of shafts substantially parallel tothe plurality of reflective elements, each shaft coupled to acorresponding reflective element; a first motor configured to rotate thearray about an axis substantially perpendicular to the plane of thearray; a second motor coupled to the plurality of shafts and configuredto rotate each of the plurality of shafts and each of one or more ofsaid reflective elements about its respective first axis of rotation;and a processor configured to: provide control signals, determined byprocessor based at least in part on the pitch and direction of thelight-admitting aperture, to operate the first and the second motor asrequired to orient the array and the reflective elements such that lightfrom a light source is reflected from a first side of the array throughthe housing and directly from the array to a target located on a secondside of the array that is opposite to the light source, the target beingremote from the array and external to the housing; receive one or morefeedback signals, wherein at least one of the one or more feedbacksignals is a video camera signal, wherein the video camera feedbacksignal indicates an illumination condition of the target located on thesecond side of the array that is opposite to the light source.
 2. Theheliostat of claim 1, wherein the plurality of reflective elementscomprises substantially rectangular elements arranged in a singlecolumn.
 3. The heliostat of claim 2, wherein each of the reflectiveelements is rotatably mounted at one or both of its shorter sides andthe first axis of rotation comprises a longitudinal axis of rotation. 4.The heliostat of claim 3, wherein each of the reflective elements ismounted to a side bracket.
 5. The heliostat of claim 4, wherein the sidebracket is configured to house a drive mechanism configured to transmitthe respective reflective elements a motive force provide by the secondmotor in a manner that causes the reflective elements to be rotate abouttheir respective axes of rotation.
 6. The heliostat of claim 1, whereinthe array of reflective elements is mounted in an annular housing. 7.The heliostat of claim 6, wherein the first motor is configured to afirst rotate the array about an axis substantially perpendicular to theplane of the array by rotating the annular housing about an annular axisof the housing.
 8. The heliostat of claim 1, wherein the processorcomprises a personal computer (PC) or other computer.
 9. The heliostatof claim 8, wherein the processor is configured to provide said controlsignals by installing and running on the computer software comprisingcomputer instructions which when executed by the processor cause theprocessor to determine a position of the sun and to compute and transmitsaid control signals.
 10. The heliostat of claim 1, wherein theprocessor comprises a mobile device.
 11. The heliostat of claim 1,wherein said processor is responsive to wireless communications receivedfrom a mobile device.
 12. The heliostat of claim 1, further comprising aglobal positioning system (GPS) device configured to provide one or moreof latitude, longitude, date, and time of day information to theprocessor.
 13. The heliostat of claim 1, further comprising a firstposition sensing device configured to detect a rotational position ofthe array about the perpendicular axis.
 14. The heliostat of claim 13,wherein the processor is configured to receive a first feedback signalfrom the first position sensing device and use the first feedback signalto generate said control signals to operate the first motor as requiredto orient the array such that the respective axes of rotation of thereflective elements are substantially perpendicular to an azimuth to thesun.
 15. The heliostat of claim 13, further comprising a second positionsensing device configured to detect a rotational position of areflective element about its first axis of rotation.
 16. The heliostatof claim 15, wherein the processor is configured to receive a secondfeedback signal from the second position sensing device and use thesecond feedback signal to generate said control signals to operate thesecond motor as required to rotate the reflective element about itsfirst axis of rotation to position the reflective element such that avector orthogonal to a reflective surface of the reflective elementsubstantially bisects an angle between a first vector from thereflective surface to the sun and a second vector from the reflectivesurface to a target to which light of the sun is to be reflected. 17.The heliostat of claim 1, further comprising an accelerometer,magnetometer, or other sensor configured to detect and provide to saidprocessor a pitch angle of the heliostat.
 18. The heliostat of claim 1,wherein said processor is configured to receive from an device externalto the heliostat an input value to be used to determine said controlsignals.
 19. The heliostat of claim 18, wherein said input valuecomprises a pitch angle and said device determines said pitch angleusing an accelerometer or other sensor of said device.
 20. The heliostatof claim 18, wherein said device includes an app or other functionalityto steer the heliostat manually and said input value is determined by auser manually steering to a target a beam emitted by the heliostat. 21.The heliostat of claim 1, further comprising a housing in which thearray is mounted and a frame to which the housing is rotatably mounted;and wherein said second motor is mounted on or within said housing. 22.The heliostat of claim 21, further comprising one or more photovoltaiccells mounted on or within the housing and configured to provide powerto said second motor.
 23. The heliostat of claim 1, wherein the one ormore feedback signals includes at least one of a light detecting deviceor a surveillance device.